You normally have to have residency in the US State you want to file the divorce in.
Luckily, Guam only requires 7 days "residency" to file for divorce there.
Fly in, meet with the divorce lawyer to get the paperwork together. Be a tourist for 7 days and on day 8, file the papers.
As long as she agrees and signs the paperwork, you're good to go.
I would recommend doing a Google search for Guam Divorce Lawyers to get more information.
Good luck!